This study is designed to show a relationship between lidocaine induced convulsions and changes in brain amines, i.e., serotonin, norepinephrine, and dopamine. Approximately ll20 male Sprague-Dawley rats will be used and only rat brain regions will be analyzed (when appropriate) for the three amines. Brain regions to be analyzed consist of the cerebral cortex, striatum, midbrain, hypothalamus, cerebellum, and pons-medulla oblongata. Homogenization of brain, extraction of the three amines and development of the serotonin fluorophore are modifications of the method described by Maickel et al., while the method of oxidation and measurement of norepinephrine and dopamine fluorophores is that described by Chang. A total of fourteen experiments are planned and consist of: 1) Dose-response curves with lidocaine challenge and manipulation of brain serotonin; 2) Dose-response curves with lidocaine challenge and manipulation of brain norepinephrine and dopamine; 3) Time-course measurement of steady-state levels of the three amines in brain regions with lidocaine challenge; 4) Synthesis rate of serotonin in brain regions with tranycypromine alone and with lidocaine; 5) Synthesis rate of serotonin in brain regions with probenecid alone and with lidocaine; 6) Time-course depletion of norepinephrine and dopamine in brain regions by alpha-methyl-p-tyrosine alone and with lidocaine; 7) Time-course depletion of norepinephrine in brain regions by FLA-63 alone and with lidocaine; 8) Repeat of the seven experiments with the drug procaine instead of lidocaine. The over-all objective is to characterize the mechanism of induction of local anesthetic seizures at the level of a brain pathway in a particular region of rat brain.